Catalytic process



Patented Sept. 21, 1943 CATALYTIC PROCESS Friedrich Franz Nerd, Bronx,N. 1., assignor to Baker & Company, Inc, Newark, N. J., a cor-- iporation of New Jersey No Drawing. Application February 15, 19.43,

Serial No. 475,972

Claims.

This invention relates to catalysts and catalytic processes and isconcerned in particular with catalytic processes involving theutilization of colloidal platinum metal catalysts.

This application is a continuation in part of my application Serial No.376,331, filed January 28, 1941.

It is one object of this invention to provide a catalyst of a metal ofthe platinum group which shall be more emcient than other such catalystsas heretofore known. It is another object of this invention to provide acatalyst of colloidal pleti num metal which shall have great stabilityand high catalytic activity and performance. It is a further object ofthis invention to provide such improved catalysts for catalyticprocesses such as oxidation, polymerization, synthesis, hydration anddehydration, hydrogenation and dehydroenation, and the like processes.The prime ob-= iect of this invention is, therefore, the reaction ofsubstances in the presence of a colloidal plati= num metal catalyst insuch manner that the emciency of such catalytic reaction is enhanced.

Hydrogenation processes for instance involve the reaction of organiccompounds, for instance fats, oils, nitro-compounds, etc., withhydrogen, for the purpose of adding hydrogen to the organic compound, orfor the purpose of reducing the organic compound with or without thesimultaneous addition of hydrogen thereto. Such processes may,therefore, involve, for instance, the hydrogenation of compounds havinga carboncarbon or carbon-nitrogen double bond or the reduction of ketoor aldehyde groups, processes which are of particular importance in thehydro- Eenatlon of fats and 011s in the manufacture of -terpenes,alkaloids, therapeutics and vitamins.

as well as in the hydrogenation of unsaturated hydrocarbon compounds inthe petroleum industry.

It is, of course, known to carry out catalytic reactions in the presenceof platinum metal catalysts. In such case the sols oi the catalyst metalare used in dispersion in various suitable solvents and are accompaniedin such solvent by a so-called protective colloid which serves tostabilize the sol of the metallic platinum metal catalyst. The substanceto be catalyzed is, likewise, introduced into such solvent containingthe colloidal platinum metal catalyst, or the solvent containing thecolloidal platinum metal catalyst is mixed with the substance to becatalyzed, and the reaction takes place under the influence of and inthe presence of the catalyst.

Protective colloids as heretofore used in con= nection with renownplatinum metal memes comprise such substance'sas gum arabic, gelatin,

lysalbinic orprotalbinic salts, cholesterole or isocholesterole or thelike. The presence of such protective colloids aiiects, however, thecatalytic activity of the colloidal catalysts in such manner that thestability produced is accompanledby a corresponding weakening of thecatalytic activity, whereby the catalytic activity is affected in ratioto the-stability produced by the protective colloid. In general the goldnumber (Zsigmondy) is taken as a rough indication of the protectiveaction of a protective colloid, so that the lower the gold number thebetter the protective effect but the more the catalytic activity isdeleteriously affected.

I have found that the efliciency of the catalytic reaction can beincreased by carrying out the reaction in the presence of a colloidalplatinum metal catalyst accompanied in its solvent by a syntheticorganic polymer. acting asva protec-- tive colloid, instead of by anatural protective colloid as heretofore employed, in that solutions ofcolloidal platinum metal and synthetic organic polymers combine highstability with high catalytic activity. The degree of polymerization ofsuch synthetic organic polymers does not appear to be critical althoughas a general rule I found that a higher degree of polymerizationexpressed itself in higher catalytic activity.

The synthetic organic polymer acting as protective colloid for thecolloidal platinum metal catalyst must be homogeneous and non-resinousand must be soluble in the particular catalyst sol-"' vent employed.Resins, plastics. and the like nonhomogeneous combinations are notsuitable for use as protective colloids.

I have found particularly suitable for use as protective colloids forcolloidal platinum metal catalysts such synthetic organic polymers asfor instance vinyl and acrylic polymers and among them, for instancemonomere compounds such as acrylic acid and polymerized compounds suchas polyvinyl alcohol, polyacrylic acid and esters, such as methyl,butylor propyl esters, of polyacrylic acid. Other polymerized syntheticorganic compounds, such as methylmethacrylate, polyvinyl acetate,polyvinyl acetals, have'also been found to be highly useful. While 'Iprefer to employ synthetic organic compounds belonging to the groupconsisting of vinyl and acrylic polymers, my invention is not limited tomembers of such restricted group, as I may employ with favorable resultsany other homogeneous non-resinous synthetic organic polymer soluble inthe solvent of the colloidal platinum metal catalyst. In this connectionI may mention, for instance, dipentene or inactive limonene.

The catalyst employed in accordance with the invention comprises,therefore, a colloidal solution of platinum metal and a syntheticorganic polymer, wherein the synthetic organic polymer acts as aprotective colloid for the colloidal platinum metal. The solvent for thecolloidal platinum metal and the synthetic organic polymer comprises anysuitable liquid medium such as water, alcohol, acetic acid,hydrocarbons, etc. The catalytic platinum metal may be platinum orpalladium or any other suitable member of the platinum group and thecatalyst solution may contain one or more metals of the platinum groupin colloidal form either alone or together with other catalytic ornon-catalytic substances which may, for instance, increase, promote orotherwise be beneficial to the catalytic process. Thus I have found, forinstance, that the catalyst solution may further contain vanadium in astate of lower valency, whereby less colloidal platinum metal is"necessary to produce the same result produced by larger quantities .ofcolloidal platinum metal without the .presence of such lowervaliant-vanadium, such catalyst being more particularly described in myco-pending application, Serial No. 376,332, filed January 28, 1941.

In order to illustrate the high efiiciency of catalytic reactions in thepresence of catalysts of colloidal platinum metal and synthetic organicpolymers, reference is made to the following experiments with a shakerhaving a speed of about 250 oscillations per minute with an eccentricityof 1.75" or a total stroke of 3.5".

I found for instance, with a solution of 1 cc. nitrobenzene, 50 cc. 50%alcohol and 1 gr. sodium hydroxide, that such solution in 5 min. absorbs135 cc. hydrogen, with a catalyst of mg. col-' loidal palladium and 100mg. tragacanth, 137 cc. hydrogen with a catalyst of 20 mg. colloidalpalladium and 100 mg. gum arabic, and 370 cc.

hydrogen with a catalyst according to my invention of 20 mg. colloidalpalladium and 100 mg. polyvinyl alcohol. This experiment shows that witha given quantity of colloidal catalyst and with a given quantity ofprotective colloid the catalyst according to my invention developsgreater catalytic activity than colloidal catalysts heretofore known; Ina similar experiment the solution in 5 min. absorbed 290 cc. hydrogenwith a catalyst of 10 mg. colloidal palladium and 100 mg. polyvinylalcohol as protective colloid as compared with an absorption of only 65cc. hydrogen with a catalyst of 10 mg. colloidal palladium and 100 mg.gum arabic, so that even smaller quantities of the catalyst according tomy invention exhibit an activity considerably higher than likequantities of catalyst as heretofore known.

In general, with colloidal catalysts as heretofore known, the catalyticactivity increases with increasing dilution of the protective colloid. Ihave found, however, that in the catalyst according to my invention thecatalytic activity tends to increase with increasing amounts ofprotective colloid. Thus I found, for instance, with a nitrobenzenesolution as previously described and a catalyst of 10 mg. colloidalpalladium, that the solution in 5 min. absorbs 155 cc. hydrogen in thecase of 5 mg. polyvinyl alcohol, 230 cc. hydrogen in the case of mg.polyvinyl alcohol, 290 cc. hydrogen in the case of 100 mg. polyvinylalcohol,

and 380 cc. hydrogen in the case of 250 mg. polyvinyl alcohol. There isa. maximum catalytic eifect at a more or less definite maximumconcentration of synthetic protective colloid, which, however, maydiifer with different protective colloids and the manufacture thereof.

Similar high activity, combined with great stability, was observed inother hydrogenation processes. -A catalyst of 10 mg. colloidal palladiumwith 250 mg. polyvinyl alcohol caused for instance the absorption of1'70 cc. hydrogen in 15 min. and 260 cc. hydrogen in 35 min. in asolution of 10 gr. castor oil (iodine #84) in a neutral medium, and of190 cc. hydrogen in 15 min. and 355 cc. hydrogen in 35 min. in asolution of 10 gr. fish oil (iodine #1295) in a neutral medium.

The colloidal catalyst may be prepared in any suitable manner. I may,for instance, dissolve a platinum metal compound in a solution of thesynthetic polymer and then convert the platinum metal compound intocolloidal platinum metal. In one specific example of one method ofpreparing such catalysts I may take for instance 12.5 cc. of a 2%aqueous solution of polyvinyl alcohol, add 1 cc. water, and dissolvetherein 1 cc. of a 1% platinum chloride solution; I may then add 0.5 cc.of a 4% sodium carbonate solution to convert the palladium to thehydroxide, adding a desired solvent, such as water or alcohol, andsubsequently reducing the palladium hydroxide to colloidal palladium bythe introduction of hydrogen, although the polyvinyl alcohol itself iscapable of reducing the solution of palladium chloride to colloidalpalladium even in the absence of hydrogen.

A palladium methacrylate catalyst may be prepared, for instance, byproviding 20 cc. of a 2% glacial acetic acid solution ofmethylmethacrylate, adding 29 cc. of glacial acetic acid, and thenadding 1 cc. of a 1% palladium chloride solution,,and subsequentlyreducing the palladium compound to colloidal palladium. It will beunderstood, however, that the colloidal solution of platinum metal andsynthetic organic polymer maybe produced by othersuitable methods. I

Natural protective colloids, as heretofore used, comprise an aggregationof different related chemical compounds of similar nature. Theirpropertiesare not easily and not always reproducible in a uniform mannerand they affect detrimentally the catalytic activity of the colloidalmetal which they accompany.

The protective colloids accompanying the colloidal metal of the platinumgroup to form the catalysts according to this invention are syntheticand, preferably, highly polymerized compounds, and constitute singlechemical entities. Their properties are easily-and uniformlyreproducible and increase rather than decrease ,the catalytic activityof the colloidal metal of the platinum group which they accompany, whileyet conveying great stability to the colloidal metal, thereby resultingin a catalyst of greater stability and higher catalytic activity than inthe case of catalysts heretofore known. The nature of my catalystaccompanied by the protective colloids of the type described is suchthat not only pure hydrogen may be used in hydrogenation processes, butalso mixtures of hydrogen with carbon monoxide, as in the well knownwater gas. or even carbon monoxide alone. a property not previouslyassociated with colloidal platinum metal catalysts. A further advantageof my catalysts, as distinguished from colloidal catalysts heretoforeknown, is that they can be used in acid, neutral as well as alkalinemedia. Compounds such as acrylic acid are suitable in -barticular foruse in organic media, whereas compounds such as polyvinyl alcohol areparticularly useful in solutions which are atleast in part The syntheticand, preferably, highly polymerized organic compound colloids formingpart of the catalyst according to this invention may be used in variousconcentrations. I believe that one reason for the beneficialcharacteristics of my novel catalyst is the great dispersion of the prtective colloid and therewith of the catalyst metal, a dispersion fargreater than that of the natural colloids heretofore used. The particlesize of the protective colloid accompanying my catalyst can be changedby freezing without alteration of the structure thereof. However,freezing may result in aggregation of particles as well as indisaggregation, and therewith greater dispersion, depending on theconcentration of the solution. By freezing for instance a 2% solution ofpolyvinyl alcohol and the like I obtain an aggregation, whereas byfreezing for instance a 0.1% solution of the same protective colloid Iobtain a disaggregation. While I have not determined the exact dividingline inthe concentration of solutions below which freezing causesdisaggregation and above which freezing causes aggregation, I believe onthe basis of experiments, that the dividing zone is at a concentrationof between 0.5% and 1%. The freezing itself' may be carried out at anysuitable temperature for the desired length of time. I have carried outsuch freezings for from minutes to 3 hours at temperatures such as --5C., -1'l 0., 18 0., and -78 C., and have found all such temperaturessatisfactory to produce substantially the same results. I may freeze asolution containing only the protective colloid, or I may freeze asolution containing both the protective colloid and the colloidalplatinum metal. The aggregation or disaggregation of the colloidalparticles does .not influence the degree of polymerization of theprotective colloid.

By thus freezing the protective colloid, with or without simultaneousdispersion of the colloidal platinum metal, I may thus further increasethe catalytic activity of such catalysts in concentrations of not morethan about 0.5% or about 1%. In hydrogenating for instance anitrobenzene solution as previously stated a catalyst of mg. colloidalpalladium, mg. polyvinyl alcohol (Du Pont 488) in a 0.1% solutionabsorbed in 8 min. 330 cc. hydrogen without freezing and 397 cc.hydrogen after having been frozen and then thawed. It will be understoodthat I recommend freezing only for low concentrations, as I have foundthat freezing of high concentrations and resultant aggregation ofcolloidal particles tends to produce a decrease in catalytic activity;thus in hydrogenating for instance a nitrobenzene solution as previouslystated a catalyst of 10 mg. colloidal palladium with 150 mg. polyvinylalcohol (Du Pont 488) in a 2% solution absorbed in 8 min. 440- cc.hydrogen without freezing and 415 cc. hydrogen after having been frozenand then thawed. It will be apparent, therefore, that highconcentrations of the synthetic colloids formin part of my novelcatalyst are always preferable 5 to low concentrations and that wherelow concentrations have to be used for some reason the catalyticactivity can be increased by freezing.

The expression "catalyzing chemical com pounds in the liquid phase," ashereinafter used.

10 refers to thereactlng of chemical compound by contacting suchcompound with the platinum metal catalyst herein described dissolved ina liquid medium, as by introducing the chemical compound or compoundsinto the solvent con- 15 taining the catalyst. or by introducing thesolvent containing the catalyst into the subst llcd' to be catalyzed ora solution containing such substance.

What I claim is:

1. The method of catalytically hydrogenating chemical compounds in theliquid phase comprising reacting the chemical compound with hydrogenv inthe presence of a catalyst comprising a colloidal solution of a metal ofthe platinum group and a homogeneous non-resinous synthetic organicpolymer, said organic polymer acting as a protective colloid for saidcolloidal metal of the platinum group.

2. The method of catalytic'ally hydrogenating a chemical compound in theliquid phasecomprising reacting. the chemical compound {with hydrogen inthe-presence of a catalyst comprising a colloidal solution of a metal ofthe platinum group and a synthetic organic polymer of the groupconsisting of vinyl and acrylic polymers, said organic polymer acting asa protective colloid for said colloidal metal of the plat!- num group.

3. The method of catalytically hydrogenating' 4o chemical compounds inthe liquid phase comprising reacting the chemical compound with hydrogenin the presence of a catalyst comprising a colloidal solution of a metalof the plattnum group and polyvinyl alcohol, said polyvinyl alcoholacting as a protective colloid for sa colloidal metal of the platinumgroup.

4. The method of catalyticallyhydrogenating chemical compounds in theliquid phase com prising reacting the chemical compound with hy= drogenin the presence of a catalyst comprising a colloidal solution ofpalladium and a homogeneous non-resinous synthetic organic polymer,said'organic polymer acting as a protective c01- loid for said colloidalpalladium.

5. The method of catclytically hydrogenating a chemical compound in theliquid phase comprising reacting the chemical compound with by drogen inthe presence of a catalyst comprising a colloidal solution of palladiumand a synthetic organic polymer of the group consisting of vinyl andacrylic polymers, said organic polymer acting as a protective colloidfor said colloidal palladi FRIEDRICH FRANZ N ORD.

